im not going to put any actual math into this ... im a nerd but im running on fumes right now if people wanna spitball with their own math, be my guest.Sublight engines could be divided into two, possibly three sections.

Maneuvering thrusters - increases rate of turn of ships (by X% of the base rate of turn.) - could be useful if you want to fix the fact that the ships can literally hyperspace from any facing direction, which will be bit*hed about in multiplayer when you guys release this.

Sublight Speed - Increases movement rate by X point(s) (or %) (again, based on X value of the ships base speed, could even be decimal points for larger ships) could also be extended to add acceleration into the game rather than have your ships start at their max speed when you give them an order, for added realism etc.

Evasion - gives ships, based on size (X) a % chance (Y) to avoid damage from an attack, or "evade" it alltogether (would be higher for frigates)

Just followed your example, shout loud enough and someone will eventually take notice. - Garrus